When transmitting a pulse signal through an electrical wire, an LVDS system is known as a transmission method for preventing a signal error due to the influence of external noises on the electrical wire (for example, JP2002-237853A) In the case of this LVDS system, a transmission-side circuit transmits a pulse signal to be transmitted as two pulse signals of a positive phase (+side) and negative phase (−side) (that is, as a differential signal). A transmission line of a pair of two lines is frequently used for transmission. Moreover, the receiving-side circuit obtains an original pulse signal by receiving two pulse signals as differential inputs.
For example, when the level of a +signal transmitted from the transmission-side circuit to the reception-side circuit is higher than the level of a −signal as shown in FIG. 9 in the case of JP11-313114A, the level becomes “1” but when the level of the −signal is higher than the level of the +signal, the level becomes “0”. In JP11-313114A, a signal level has either of 1.2 V and 1.5 V.
In the case of the conventional LVDS system described above, the number of signal lines used to send/receive a serial signal is fixed. This case has a disadvantage that it is impossible to select the number of channels and a data rate optimum for the impedance of a signal line used for transmission/reception.
The present invention is made to solve the problems of the above prior art and its object is to provide an LVDS system capable of selecting the number of channels and a data rate optimum for the impedance of a signal line for transmission/reception, its transmission-side circuit, and it reception-side circuit.